[Halld-tagger] [EXTERNAL] Re: microscope pictures with green / blue laser

[Richard T. Jones]

Beni,

Yes we are around 400ps rms in the TAGM now, but as Hovanes says it was
closer to 200ps when the device was first installed. This shows the degree
to which its light output has now degraded. But I think the PS coarse
counters were always at this same level of 400-500ps.

-Richard J.


On Fri, Oct 17, 2025 at 6:48 AM zihlmann via Halld-tagger <
halld-tagger at jlab.org> wrote:

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> Hi Hovanes,
> with my naive plugin looking at tagger time minus RF time I see a sigma of
> about 400ps.
> nothing sophisticated to optimize the result.
> I see similar sigmas for the PS tiles times where I use the PS coarse
> counters as time reference.
> Also, the PS tiles do not have TDCs only fADCs.
>
> cheers,
> Beni
>
> On 10/16/25 19:02, Hovanes Egiyan wrote:
>
> Hi Beni,
>
> Thanks for the nice pictures.
>
> GlueX NIM paper quotes 230ps for the timing resolution for TAGM.
>
> Best,
>     Hovanes.
>
> On Thu, Oct 16, 2025 at 4:06 PM zihlmann via Halld-tagger <
> halld-tagger at jlab.org> wrote:
>
>>
>> Hi All,
>>
>> I added several more pictures and "movies" to the photo album of the
>> tagger microscope:
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__photos.app.goo.gl_Q9To4SutT7854mmV6&d=DwIFaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=-MwMW0sKroUIjy-Lh9rb3KzmWIgdcbbr9_jez8RLmto&m=rMwvMqK1euAEfP4G46eSIxNr-_ndnPU3anhIfXpXO7yFanAXvm2vQvJ_QGDecThf&s=-gRLmp9sUJvio8g1xpR8DiIQQtFhbKYRciftb9jJN-k&e= 
>> I highlighted a few points with three picked out pictures (see attached
>> pdf file)
>> With the green laser shining into the front face of the scintillator one
>> can nicely see
>> where the "losses" are in the fiber front face, in the fused section and
>> along the light guide.
>>
>> In addition, I looked at the timing resolution of the pair spectrometer
>> tiles and I find in
>> my quick and dirty approach very similar timing resolutions as for tagger
>> microscope
>> of order 300ps.
>>
>> cheers,
>> Beni
>>
>>
>>
>>
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